The present invention relates to improvements in apparatus for removing contaminants, such as sludge, from fluids which are circulated in centrifugal pumps, turbines and like fluid flow machines wherein solid contaminants must be kept away from contact with one or more sensitive components including bearings, seals and the like. More particularly, the invention relates to improvements in apparatus which can be installed in centrifugal pumps, turbines or like machines in regions between first and second spaces respectively containing contaminated and purified fluids to ensure that the second space receives a fluid (primarily liquid) which is devoid of any contaminants or wherein the percentage of contaminants is reduced to an acceptable value.
Many machines which convey one or more streams of a contaminated fluid (hereinafter, the fluid will be referred to as liquid) must be provided with means for intercepting at least a certain percentage of solid contaminants upstream of certain sensitive components which are likely to be damaged or destroyed by solid impurities. Typical examples of such machines are sludge pumps whose purpose is to convey a contaminated liquid but which do contain several parts that must be shielded from some or all of the impurities in spite of the fact that they necessarily come in contact with the conveyed liquid. Heretofore known cleaning or separating apparatus include those which are provided with deflectors serving to cause the impurities to bypass the bearings, seals and analogous sensitive parts. In many instances, such deflectors rely on the action of centrifugal force, on the establishment of meandering paths for the flow of contaminated liquid and/or on similar expedients. Care must be exercised to ensure that stoppage of the machine will not result in settling of floating heavier impurities or rise of lightweight contaminants and possible accumulation of settled or risen impurities in regions from which the impurities will or are likely to reach the sensitive parts on resumption of operation of the machine, i.e., intermittent operation of the machine should not entail relatively large accumulations of impurities in the space or spaces which lead to bearings, seals or the like.
Heretofore known cleaning or separating apparatus of the above outlined character are not entirely satisfactory for a variety of applications. Therefore, the cleaning action of such apparatus is often implemented by addition of clean liquid which has been relieved of impurities at a locus remote from the machine or which was never contaminated. The clean liquid can constitute a sealing liquid (also called injection medium) which is conveyed from the outside and is used in or in connection with many types of seals for pumps or the like. Alternatively, the liquid which flows toward the sensitive part or parts of a pump, turbine or a like fluid flow machine can be caused to pass through one or more filters, for example, under the influence of the normally existing pressure differentials in such types of machines. If the pressure differential which develops when the machine is in use does not suffice, the machine can be equipped with auxiliary circulating means which causes or cause the liquid (or a portion of the liquid) to pass through one or more filters while on the way into contact with sensitive components of the machine or while flowing through a bypass whose outlet leads into the chamber for non-contaminated liquid. Such methods have met with reasonable success but the apparatus for the practice thereof exhibit a number of serious drawbacks which prevent them from finding application in a number of machines. Thus, if the filter or filters are installed in the interior of the machine, contaminated liquid (i.e., liquid which is still laden with lightweight and/or relatively heavy impurities) must be permitted to enter the pump proper. This can result in deposition and accumulation of prematurely separated contaminants in the path which leads into the filtering unit. Moreover, the contaminants are likely to be recirculated more than once with attendant wear upon the parts which come in repeated contact therewith prior to final or actual removal of intercepted impurities from the machine.
As a rule, the space which contains the contaminated liquid cannot be completely segregated from the space for reception and storage of cleaned liquid. Thus, at least some leakage will take place in highly reliable seals and such leakage is likely to lead to admission of a certain amount of impurities into the space for clean liquid. Moreover, while the two spaces might be practically completely sealed from each other in normal operation of the machine, pronounced deviations of pressure from anticipated pressure and the resulting more pronounced pressure differentials are likely to entail the admission of higher percentages of contaminants into the space which is supposed to contain clean liquid. For example, the consumer of pressurized liquid which is connected to the outlet of a centrifugal pump is likely to influence the pressure differential in the interior of the pump to such an extent that contaminants tend to penetrate into the region of seals, bearings or the like when the operation of the consumer entails a pronounced rise of pressure in the space for contaminated liquid and/or pronounced fluctuations of the rate of liquid flow between the two spaces.
A further drawback of conventional cleaning or separating apparatus is that removal of friction heat from the space for clean liquid often necessitates vigorous circulation of cleaned liquid therein. Also, an effective filter or system of filters is often very bulky so that it cannot be readily installed in many types of existing fluid flow machines. On the other hand, filters are likely to offer high resistance to the flow of liquid therethrough so that the apparatus must be equipped with powerful liquid circulating means which consume large quantities of energy. If the resistance of the filter or filters is high, the apparatus must be equipped with means for removing the developing heat or for cooling the cleaned liquid prior to permitting it to flow into contact with bearings, seals or the like.